This invention relates to controls for electrical apparatus and more particularly to circuit controls having electronic image display screens for producing graphics pertinent to operation of the controls.
Many devices for controlling electrical apparatus have a moveable member which the operator turns or slides in order to vary a control signal. Typically graphics are present in the vicinity of the moveable member to indicate the function of the control and to identify settings of the control along the path of travel of the member. Traditionally such graphics are permanently imprinted on a control panel or other structural component of the control device.
It has been recognized that it can be advantageous to replace the permanently imprinted graphics with changeable images produced by an electronic display screen particularly in the case of a control device which is used to control different functions of the controlled apparatus during different modes of operation of the apparatus. The display can change the graphics as needed so that they remain appropriate during each of the different control functions.
The function of the electronic display screen has heretofore been limited to that of visually presenting information to the operator, such as calibration marks, current settings, identifying labels and the like. It has not previously been recognized that an electronic display screen may serve other purposes in addition to displaying information to the operator of a circuit control device.
In one aspect of the invention, a control device for providing a control signal to electrical apparatus has at least one photosensor which detects movement of a moveable member in order to vary the control signal. The control device is disposed in front of an electronic image display screen which can display changeable images conveying information pertinent to operation of the control device. The display screen is also the light source for the photosensor or photosensors.
In another aspect of the invention, the control device further includes a display screen controller conditioned to cause display of a light pattern wherein different locations in the light pattern are viewed by the photosensor as the moveable member is moved through settings thereof. The display screen controller is further conditioned to move a light variation through the locations in the light pattern which light variation is detectable by the photosensor to produce a location sensing signal.
In another aspect of the invention, the moveable member is a stylus having an end that may be placed at a selected location in front of the image display area of the display screen. The photosensor is secured to the stylus and is oriented to view a portion of the image area that is offset the end of the stylus. In another aspect, the end of the stylus defines an axis of rotation about which the stylus may be turned. The photosensor is positioned on the stylus to view selected locations in the image display area that lie along a path which extends around the axis of rotation.
In another aspect of the invention, the moveable member of the control device is a knob which is engaged on a base that is attached to the display screen and which is turnable about an axis of rotation.
In still another aspect of the invention the moveable member is a cap which is slidable along a track, said track and cap being in front of the image display area of the image display screen. A display screen controller is coupled to the display screen and is conditioned to cause display of a light pattern which extends along the track and wherein different locations along the light pattern correspond to different settings of the control device. The photosensor is carried by the cap in position to receive light from the different locations along the light pattern as the cap is moved therealong.
The invention enables photoelectric tracking of movement of the moveable member of a circuit control device using light produced by an electronic display screen which may also display graphics pertinent to operation of the control device. A separate light source is not needed. This eliminates certain hardware components and electrical conductors heretofore needed for photoelectric sensing of control member movement. Depending on the particular type of control device, this variously reduces structural complication and/or bulk and/or manufacturing cost of the control device. In one form of the invention this provides what may be termed virtual control devices in which settings of the control device are identified by images on the display screen and a moveable image identifying the current setting of the control device. The setting may be changed by applying the tip of a stylus to the display screen and then twisting the stylus.
The invention, together with further aspects and advantages thereof, may be further understood by reference to the following description of preferred embodiments and by reference to the accompanying drawings.